Rotational degrees of freedom data synthesis based on force excitation

In many structural dynamic tools, mobility matrices manipulations are foreseen. It’s understood that the full matrices, containing translational and rotational degree of freedom data are requested in order to obtain meaningful and correct results. Unfortunately the latter data that comprehend mobility function either with rotational responses or angular excitations are neglected due to the difficulties related to their measurements. In this article a method to derive RDOF data will be presented. The proposed technique relay on response data obtained with standard force excitation and on numerical matrix expansion techniques. The approach is based on the assumption that, in the surrounding of the point of interest, within the frequency range of interest, the structure behaves as a rigid body. Under this condition, if reciprocity holds, some relations between linear and rotational motions can be established and the RDOF functions due to angular excitation can be derived.